Field of the Invention
The present invention relates to a water heater, and particularly to a water heater of a latent heat recovery type capable of heating water by recovering latent heat of combustion gas.
Description of the Background Art
In a water heater, condensate may be generated as air warmed by internally generated heat is cooled at various sites. In particular, at a site where water supplied to the water heater during a hot water supply operation flows into a housing of the water heater (a water entry portion), clean water at a low temperature flows in. Therefore, generation of condensate is likely due to condensation of moisture contained in air at a relatively high temperature around the water entry portion.
In a case that the water entry portion is arranged in a bottom plate of the housing, such condensate merely flows along the bottom plate of the housing. In a case that the water entry portion is provided in a top plate of an instrument, however, condensate may drop onto an electronic component of the water heater and failure may be caused.
Conventionally, in providing a water entry portion in a top plate of an instrument, in order to prevent failure of an electric component due to drop of condensate, the water entry portion has had to be arranged in a position other than a position directly above the electric component or a cover has had to be provided between the water entry portion and the electric component below. For example, Japanese Patent Laying-Open No. 10-267278 describes a cover (a top plate portion) provided above a high voltage generation portion in order to prevent water condensed at an inner surface of a top plate of a housing of a water heater from dropping onto the high voltage generation portion of an igniter.
When such a cover only for preventing drop of condensate from the water entry portion is provided, however, the number of parts increases. Therefore, from an aspect of costs and reduction in size, drop of condensate onto an electric component is desirably prevented without requiring such a cover.
Therefore, it is possible to arrange a component other than an electric component directly under a water entry portion in order to allow drop of condensate from the water entry portion onto that component and to protect the electric component. Here, examples of a component other than an electric component arranged directly under the water entry portion include a part constituting a heat exchanger arranged generally on an upstream side and an exhaust path for combustion gas which has passed through the heat exchanger.
In the inside of a part constituting a heat exchanger and an exhaust path for combustion gas which has passed through the heat exchanger, however, combustion gas is present. When this combustion gas is cooled by condensate, moisture contained in combustion gas is condensed and drainage water is generated. This generated drainage water will corrode the part constituting the heat exchanger and the exhaust path for combustion gas which has passed through the heat exchanger.